Fluid storage tank having active integrated cooling

ABSTRACT

A fluid storage tank including heat extraction arrangements is provided. The fluid storage tank includes a passive and an active heat exchanger. A fan draws ambient air through both the active and passive heat exchangers to dissipate heat energy stored in the fluid passing through or stored within the tank.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This patent application claims the benefit of U.S. Provisional Patent Application No. 61/352,859, filed Jun. 9, 2010, the entire teachings and disclosure of which are incorporated herein by reference thereto.

FIELD OF THE INVENTION

This invention generally relates to fluid storage tanks and more particularly to fluid storage tanks configured to remove heat from the fluid stored therein.

BACKGROUND OF THE INVENTION

Many devices use fluid as a means to power other devices. For instance, many devices such as trucks, heavy equipment, construction equipment, farm equipment, etc. will utilize a hydraulic system that uses pressurized hydraulic fluid (typically oil) to run hydraulic motors, drive hydraulic cylinders, etc.

Unfortunately, as the hydraulic fluid is cycled through the system, the fluid will take on heat energy. This heat energy can be detrimental to the devices within the system such as the hydraulic motors, hydraulic pumps, hydraulic cylinders, as well as the seals or conduits for transporting the hydraulic fluid. One method to remove heat from the hydraulic fluid is to provide a larger fluid storage tank such that there is a greater surface area between the metal tank and the surrounding ambient environment, typically air, to promote increased heat transfer. Unfortunately, this provides an increased footprint in which the storage tank must be positioned relative to the vehicle. This can be problematic when trying to retrofit or improve the heat capabilities of a given system when the envelope in which the storage tank is already fixed due to prior constraints of the vehicle.

Other systems have used remote radiators through which the hydraulic fluid flows to attempt to remove heat from the hydraulic fluid. The present invention relates to improvements over the prior state of the art relating to larger storage tanks and the inclusion of a radiator system for removing heat.

BRIEF SUMMARY OF THE INVENTION

Embodiments of the present invention relate to new and improved fluid storage tanks that incorporate integrated heat exchangers to promote heat extraction from the fluid stored in the tanks. The heat exchangers may include an active and passive heat exchanger. In one embodiment, a fan is provided to direct/draw air through both the active and passive heat exchangers. In one more particular embodiment, the ambient air is first passed through the passive heat exchanger and then through the active heat exchanger.

In a further embodiment, the passive heat exchanger is at least one outer heat extraction fin extending laterally outward from a sidewall forming or bounding a part of the interior cavity of the tank. The tank may further include at least one inner heat extraction fin extending laterally into the interior cavity of the tank such that it can be contacted by fluid stored within the interior cavity. More preferably, the at least one inner heat extraction fin is substantially aligned with the outer heat extraction fin. This reduces the resistance to heat conduction from the inner fins to the outer fins.

The heat extraction fins may be perforated with apertures to promote fluid flow through the fins by either ambient air or stored fluid.

When a plurality of inner and/or a plurality of outer heat extraction fins are provided and each fin is perforated, the perforations of adjacent ones of the fins are misaligned such that a fluid flow path through the perforations is zig-zagged to further promote heat transfer to the fluid.

In one embodiment, the active heat exchanger is a liquid to air heat exchanger.

The inner and outer heat extraction fin may be welded to inner and outer surfaces of a sidewall of the tank, respectively. Preferably, the welds extend along both longitudinal surfaces of the fins to increase the heat conductivity between the fins and the sidewall.

To prevent damage to the active heat exchanger, i.e. the heat exchanger having both the ambient air and stored fluid flowing therethrough, the storage tank may further include a check valve upstream of the active heat exchanger. The check valve provides a bypass around the active heat exchanger when a predetermined pressure is attained.

In a further particular embodiment, an outlet conduit fluidly coupling an outlet of the heat exchanger to the interior cavity of the tank is configured to direct fluid flow of the stored fluid towards the inner heat extraction fin. This promotes increased heat transfer from the fluid to the inner heat extraction fin.

In a further embodiment, the passive heat exchanger further includes a first outer shroud portion attached to the tank bounding at least part of a first air flow path having a first outlet generally adjacent the fan and a first inlet spaced away from the fan. The passive heat exchanger further includes a first plurality of spaced apart outer heat extraction fins extending outward from the tank. The first plurality of spaced apart outer heat extraction fins are interposed between the first inlet and the first outlet along the air flow path and are positioned between the first shroud portion and the tank. Each of the first plurality of outer heat extraction fins include at least one aperture through which the first air flow path passes as the first air flow path extends from the first inlet to the first outlet. In an even further embodiment, the passive heat exchanger further includes a second outer shroud portion attached to the tank bounding at least part of second air flow path having a second outlet generally adjacent the fan and a second inlet spaced away from the fan. The passive heat exchanger further includes a second plurality of outer heat extraction fins extending outward from the tank. The second plurality of outer heat extraction fins are interposed between the second inlet and the second outlet along the air flow path and are positioned between the second shroud portion and the tank. Each of the second plurality of outer heat extraction fins includes at least one aperture through which the second air flow path passes as the second air flow path extends from the second inlet to the second outlet.

In one embodiment, the active heat exchanger is positioned between the first and second outlets such that air passed through the active heat exchanger is drawn from the first and second outlets such that the air passed through the active heat exchanger by the fan has first passed through at one of the plurality of first or second heat extraction fins.

In one embodiment, the first and second shroud portions are provided by a single shroud. The single shroud includes an opening between the first and second shroud portions. The opening is aligned with the active heat exchanger. The fan forces the air through the active heat exchanger and then through the opening.

In a further embodiment, a fluid storage tank including a tank and a heat extraction arrangement is provided. The heat extraction arrangement includes an active heat exchanger, a passive heat exchanger and a fan. The active heat exchanger has a fluid flow path having an outlet in fluid communication with the interior of the fluid storage tank for dispensing fluid to be stored within the tank into the tank. The active heat exchanger has an external periphery in fluid communication with the ambient air surrounding the tank. The passive heat exchanger is external to the tank and is thermally connected to the tank. The passive heat exchanger has a plurality of outer heat extraction fins extending outward in a direction extending away from an outer surface of the tank. The outer heat extraction fins are in fluid communication with the ambient air. The fan moves ambient air through both the active and passive heat exchangers. The fan first passes ambient air through the passive heat exchanger and then passes the air through the active heat exchanger.

In a further embodiment, the passive heat exchanger further includes a first outer shroud portion attached to the tank bounding at least part of a first air flow path having a first outlet generally adjacent the fan and a first inlet spaced away from the fan. The passive heat exchanger further includes a first plurality of spaced apart outer heat extraction fins extending outward from the tank. The first plurality of spaced apart outer heat extraction fins are interposed between the first inlet and the first outlet along the air flow path and are positioned between the first shroud portion and the tank. Each of the first plurality of outer heat extraction fins include at least one aperture through which the first air flow path passes as the first air flow path extends from the first inlet to the first outlet. In an even further embodiment, the passive heat exchanger further includes a second outer shroud portion attached to the tank bounding at least part of second air flow path having a second outlet generally adjacent the fan and a second inlet spaced away from the fan. The passive heat exchanger further includes a second plurality of outer heat extraction fins extending outward from the tank. The second plurality of outer heat extraction fins are interposed between the second inlet and the second outlet along the air flow path and are positioned between the second shroud portion and the tank. Each of the second plurality of outer heat extraction fins includes at least one aperture through which the second air flow path passes as the second air flow path extends from the second inlet to the second outlet.

In an even more particular embodiment, the fluid storage tank includes a plurality of inner heat extraction fins internal to the tank. Each of the plurality of inner heat extraction fins is aligned with a corresponding one of the plurality of outer heat extraction fins.

A method of extracting heat from a fluid is also provided. The method includes passing the fluid through an active heat exchanger that is external to a storage tank for housing the fluid, the active heat exchanger in fluid communication with ambient air surrounding the fluid storage tank; dispensing the fluid into the storage tank after passing it through the active heat exchanger; passing the ambient air through a passive heat exchanger thermally connected to the storage tank; and passing the ambient air through the active heat exchanger after passing it through the passive heat exchanger.

A more particular method includes passing the ambient air through a passive heat exchanger thermally connected to the storage tank and passing the ambient air through the active heat exchanger after passing it through the passive heat exchanger are performed by a same fan.

Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

FIG. 1 is a perspective illustration of a fluid storage tank 100 according to a first embodiment of the present invention;

FIG. 2 is a partial illustration of the fluid storage tank of FIG. 1 further illustrating the heat extraction arrangement thereof;

FIG. 3 is a further partial illustration of the fluid storage tank of FIG. 1 showing the electric fan of the heat extraction arrangement;

FIG. 4 is a partial illustration of the fluid storage tank 100 illustrating the internal components thereof;

FIG. 5 is a further internal illustration of the fluid storage tank of FIG. 1;

FIG. 6 is a fluid plan view of the fluid storage tank of FIG. 1;

FIG. 7 is a partial plan view of the fluid storage tank showing fluid flow paths through the heat extraction arrangement thereof;

FIG. 8 has the heat exchanger removed to illustrate the air flow through the fan of the heat extraction arrangement; and

FIG. 9 is a top view illustration of the fluid storage tank 100 having the top portion of the wrapper and the outer shroud of the heat extraction arrangement removed.

While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a fluid storage tank 100 in perspective view according to an embodiment of the present invention. The storage tank 100 includes an outer wrapper 102 having sides defining an internal cavity in which the fluid (typically hydraulic fluid) is stored. The fluid storage tank 100 includes a return inlet 104 through which the oil that has passed through the system returns to the storage tank 100. The fluid storage tank 100 further includes an outlet or suction port 106 through which fluid previously stored within the tank 100 is drawn by the system and used.

The fluid storage tank 100 includes a filtration arrangement 108. This filtration arrangement 108 stores a replaceable filter element through which the return fluid passes prior to it being deposited within the storage cavity of the storage tank 100. Other embodiments of the fluid storage tank utilizing features of the present invention need not include such a filtration arrangement 108.

The illustrated embodiment also includes a heat extraction arrangement 110 generally attached to and/or forming part of the outer wrapper 102 of the storage tank 100. The heat extraction arrangement 110 is configured to promote heat removal from the fluid stored within and passing through the storage tank 100.

The heat extraction arrangement 110 generally includes a passive heat exchanger in the form of a plurality of heat extraction fins 120 (see also FIG. 2), an outer shroud 122 for controlling airflow, an active heat exchanger in the form of heat exchanger 124 through which hydraulic fluid also flows, and a fan 126 (see FIG. 3).

The heat extraction arrangement 110 is configured to promote the dissipation of the heat within the hydraulic fluid to the ambient surroundings, e.g. the surrounding air. Heat is dissipated as the hydraulic fluid passes through the heat exchanger 124 and the ambient air is passed across the heat exchanger 124. The outer shroud 122 is used to define an airflow passage through the outer heat extraction fins 120 and then through the heat exchanger 124. The outer shroud 122 is preferably substantially sealed on the outer periphery of the outer heat extraction fins 120 on opposed ends 130, 132 of the outer shroud 122. This promotes air flow through the outer heat extraction fins 120 as it flows through outer shroud 122.

The outer heat extraction fins 120 include a plurality of airflow ports 134 (also referred to as apertures). In a preferred embodiment, the airflow port/apertures 134 of adjacent ones of the outer heat extraction fins 120 are offset from one another such that the airflow path extending laterally through and inward toward fan 126 and heat exchanger 124 is in a zig-zag flowpath. This non-linear flowpath assists in promoting increased heat transfer from the outer heat extraction fins 120 to the ambient air flowing therethrough. More particularly, this promotes increased interaction between the ambient air and the surfaces provided by the outer heat extraction fins 120.

After the ambient air passes through the outer heat extraction fins 120, the ambient air will pass through the fan 126 and then outward away from the wrapper 102 and through the heat exchanger 124.

As such, the entire flow path of the ambient air through the heat extraction arrangement 110 generally starts with passing through the outer heat extraction fins 120, which may be considered a passive heat exchangers, then it passes through fan 126 and then outward through heat exchanger 124, which may be considered an active heat exchanger.

With reference to FIGS. 2 and 3, the heat exchanger 124 is removably connected to the fluid storage tank 100 using a plurality of connectors. In one embodiment, the connectors are a plurality of quick release connectors or non-permanent connectors such that the heat exchanger 124 can be easily removed therefrom.

Further, in one embodiment, the heat exchanger 124 is directly mounted to the outer wrapper 102 of the fluid storage tank 100. As illustrated in FIG. 3, a mounting bracket 136 helps support and/or attach the heat exchanger 124 to the outer wrapper 102. This makes for a small footprint. In this case, the heat exchanger 124 is reversed inward toward wrapper 102 relative to outer distal ends of outer heat extraction fins 120.

Further, the fan 126 is preferably a 12 volt electric fan such that it can be easily connected to the standard 12 volt power supply for typical vehicles. With reference to FIG. 4, the fan motor is mounted within a laterally inward extending pocket 138 that extends generally inward from the outer sidewall of the outer wrapper 102 to which the heat extraction arrangement 110 is mounted. This pocket 138 allows for a low profile arrangement. Further, by promoting a low profile arrangement and preventing the heat extraction arrangement 110 from extending further laterally outward from the side of outer wrapper 102, the overall footprint of the fluid storage tank 100 may be reduced and/or maintained at a same size as a fluid storage tank 100 that does not include the heat extraction arrangement. This reduced size configuration helps promote replacement of a standard fluid storage tank with the modified embodiments of the present invention. Further, the use of an electric motor, particularly a 12 volt electric motor, for the fan further promotes easy retrofit to an existing vehicle as the typical vehicle has a 12 volt electrical system present.

With primary reference to FIG. 4, the interior cavity 140 of the fluid storage tank 100 is illustrated. More particularly, three sides of outer wrapper 102, the sides that do not include the heat extraction arrangement 110, are removed. FIG. 4 illustrates that filter arrangement 108, and particularly the housing thereof, extending vertically into the internal cavity 140.

Downstream from the filter arrangement 108 is a check valve 142. The check valve will typically have an opening pressure of between about 4 and 8 psi; however, other pressure ranges can be used depending on the system in which the fluid storage tank 100 is used. This check valve 142 will open if the system experiences an increase or spike in fluid pressure to prevent damage to other components in the system, and most particularly to the heat exchanger 124.

Between the check valve 142 and the filtration arrangement 108, the fluid flow path includes a T-connector 144. Fluid conduit 146 connected to the T-connector 144 extends laterally through the sidewall 170 of the outer wrapper 102 and operably connects to an inlet end of the heat exchanger 124. As such, the fluid that will pass through the heat exchanger 124 will have previously been operably filtered through filter arrangement 108. This greatly prevents the clogging or plugging of the hydraulic fluid flow paths through the heat exchanger 124.

After the hydraulic fluid has passed through the heat exchanger 124, it will be operably returned into the interior cavity 140 of the fluid storage tank 100. A return conduit 148 is operably coupled to an outlet end of the heat exchanger 124 and extends laterally inward through the sidewall 170 of outer wrapper 102. The return conduit 148 extends downward and into a inlet chamber 150 of the interior cavity 140.

To promote heat transfer from the hydraulic fluid to the ambient surrounding air, the interior of the fluid storage tank 100 also includes a plurality of inner heat extraction fins 152. Again, the inner heat extraction fins 152 are perforated fins just like the outer heat extraction fins 120. The inner heat extraction fins 152 include a plurality of flow apertures 154. The hydraulic fluid stored within internal cavity 140 can pass through the flow apertures 154 to increase the amount of heat transfer from the hydraulic fluid to the inner heat extraction fins 152. Also, the flow apertures 154 of adjacent ones of the inner heat extraction fins are offset to cause a zig-zag flow path through the heat extraction fins 152.

The outlet end 160 of the return conduit 148 is preferably directed towards the bank of inner heat extraction fins 152 thereto. The hydraulic fluid will then be directed towards these heat extraction fins 152 to promote increased heat transfer from the hydraulic fluid to the inner heat extraction fins 152. This flow of fluid is illustrated by arrows 162. In alternative arrangements, the outlet of the return conduit 148 can be positioned such that increased flow is provided through the inner heat extraction fins 152.

The present invention includes a nucleation arrangement 164 downstream from the outlet end 160 of return conduit 148. This arrangement can facilitate extraction of entrained air stored within the fluid.

The inlet chamber 150 is generally bounded in the present embodiment by top plate 166, the nucleation plate 168 of the nucleation arrangement 164, and various sides of the outer wrapper 102.

Downstream from the inlet chamber 150 is a second bank of inner heat extraction fins 152. As such, the hydraulic fluid will flow through nucleation arrangement 164 and then through the second bank of inner heat extraction fins 152 prior to exiting through outlet 106.

In one embodiment, a same number of inner heat extraction fins 152 and outer heat extraction fins are provided. This allows for a substantially similar amount of interior surface area provided by the inner heat extraction fins 152 as is provided by the outer heat extraction fins 120.

In one embodiment, the inner heat extraction fins 152 extend the entire width w (see FIG. 1) of the fluid storage tank 100. In an alternative embodiment, the inner heat extraction fins 152 only extend a portion of the width w.

In one embodiment, there is a corresponding inner heat extraction fin 152 for each outer heat extraction fin 120. As such, in the illustrated embodiment of FIG. 4, there are 10 inner heat extraction fins 152 and thus there would be 10 outer heat extraction fins 120. Further, the corresponding inner and outer heat extraction fins 152, 120 are substantially aligned with one another to promote conductive heat transfer from the inner heat extraction fins 152 to the outer heat extraction fins 120. To reduce the amount of potential leak paths, the sidewall 170 to which the heat fins 120, 152 are mounted is continuous. As such, the heat extraction fins 120, 152 are welded thereto. This welding also reduces the resistance of heat transfer from the fins through the sidewall 170. In one embodiment, top plate 166 is not such that the lower portion of the inner heat extraction fins 152 extends thereinto.

Turning now to FIG. 5, adjacent ones of inner or outer heat extraction fins 152, 120 may be spaced at different intervals. In one embodiment, the spacing s is between about ½ and 1 inch, and more preferably about ⅝ inch.

During manufacture, each heat extraction fin is welded on both sides along the vertical edge having length L thereof. The thickness t of an individual heat extraction fin 120, 152 is preferably between about 3 and 8 millimeters.

During operation, hot returned hydraulic fluid will enter the fluid storage tank 100 through return inlet 104 and then pass through filter arrangement 108. After being filtered, the hydraulic fluid will then pass through T-connector 144 and, if pressure is low enough, through supply conduit 146 toward heat exchanger 124. The high temperature hydraulic fluid will then pass through heat exchanger 124. The high temperature hydraulic fluid will then be converted to intermediate or low temperature hydraulic fluid as ambient air is passed across heat exchanger 124 to cool the hydraulic fluid. The intermediate temperature fluid will then be dispensed into internal cavity 140 via return conduit 148. The intermediate temperature hydraulic fluid will then transfer heat to heat extraction fins 152 to further extract heat therefrom. This heat will be conducted to outer heat extraction fins 120. The same air that is being drawn by fan 126 is passed across outer heat extraction fins 120 to further promote heat removal from the fluid storage tank 100. The cool hydraulic fluid will then be drawn out of the fluid storage tank 100 via suction or outlet port 106. As the hydraulic fluid passes through the internal cavity 140, it can pass through or across various members of banks of heat extraction fins 152.

In some embodiments, the check valve may be directly plumbed to the return/outlet conduit 148 with an additional conduit/bypass path so that fluid that bypasses the heat exchanger 124 follows a desired flow path through the storage tank 100, i.e. through the nucleation arrangement in the illustrated embodiment.

In some embodiments, the outer shroud or heat extraction arrangement may be plumbed within the ambient air to a source of cooler air, such as a wheel well of a vehicle for instance.

All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 

1. A fluid storage tank comprising: a tank; a heat extraction arrangement including an active heat exchanger, a passive heat exchanger, and a fan for moving ambient air through both the active and passive heat exchangers.
 2. The fluid storage tank of claim 1, wherein the air flow provided by the fan first passes through the passive heat exchanger and then through the active heat exchanger.
 3. The fluid storage tank of claim 2, wherein the passive heat exchanger is at least one outer heat extraction fin extending laterally outward from a sidewall forming at least part of the interior cavity of the tank.
 4. The fluid storage tank of claim 3, further including at least one inner heat extraction fin extending laterally into the interior cavity of the tank such that it can be contacted by fluid stored within the interior cavity.
 5. The fluid storage tank of claim 4, wherein the at least one inner heat extraction fin is substantially aligned with the outer heat extraction fin.
 6. The fluid storage tank of claim 4, wherein the heat extraction fins include a plurality of apertures.
 7. The fluid storage tank of claim 6, including a plurality of inner and a plurality of outer heat extraction fins that are perforated, wherein the apertures of adjacent ones of the fins are not aligned such that a fluid flow path through the apertures is zig-zagged.
 8. The fluid storage tank of claim 1, further including a nucleation arrangement within an interior cavity of the tank, the nucleation arrangement fluidly downstream of the active heat exchanger.
 9. The fluid storage tank of claim 1, wherein the active heat exchanger is a liquid to air heat exchanger.
 10. The fluid storage tank of claim 4, wherein the at least one inner and at least one outer heat extraction fin are welded to a sidewall of the tank.
 11. The fluid storage tank of claim 1, further including a check valve upstream of the active heat exchanger, the check valve providing a bypass into an interior cavity of the tank when a predetermined pressure is attained.
 12. The fluid storage tank of claim 4, further including an outlet conduit fluidly coupling an outlet of the heat exchanger to the interior cavity of the tank, the outlet conduit directing fluid flow towards the at least one inner heat extraction fin.
 13. The fluid storage tank of claim 2, wherein the passive heat exchanger further includes a first outer shroud portion attached to the tank bounding at least part of a first air flow path having a first outlet generally adjacent the fan and a first inlet spaced away from the fan, the passive heat exchanger further including a first plurality of spaced apart outer heat extraction fins extending outward from the tank, the first plurality of spaced apart outer heat extraction fins interposed between the first inlet and the first outlet along the air flow path and positioned between the first shroud portion and the tank, each of the first plurality of outer heat extraction fins including at least one aperture through which the first air flow path passes as the first air flow path extends from the first inlet to the first outlet.
 14. The fluid storage tank of claim 13, wherein the passive heat exchanger further includes a second outer shroud portion attached to the tank bounding at least part of a second air flow path having a second outlet generally adjacent the fan and a second inlet spaced away from the fan, the passive heat exchanger further including a second plurality of outer heat extraction fins extending outward from the tank, the second plurality of outer heat extraction fins interposed between the second inlet and the second outlet along the air flow path and positioned between the second shroud portion and the tank, each of the second plurality of outer heat extraction fins including at least one aperture through which the second air flow path passes as the second air flow path extends from the second inlet to the second outlet.
 15. The fluid storage tank of claim 14, wherein the active heat exchanger is positioned between the first and second outlets such that air passed through the active heat exchanger is drawn from the first and second outlets.
 16. The fluid storage tank of claim 15, wherein the first and second shroud portions are provided by a single shroud, the single shroud including an opening between the first and second shroud portions, the opening aligned with the active heat exchanger, the fan forces the air through the active heat exchanger and then through the opening.
 17. A fluid storage tank comprising: a tank; a heat extraction arrangement including: an active heat exchanger having a fluid flow path having an outlet in fluid communication with the interior of the fluid storage tank for dispensing fluid to be stored within the tank into the tank, the active heat exchanger having an external periphery in fluid communication with the ambient air surrounding the tank; a passive heat exchanger external to the tank thermally connected to the tank, the passive heat exchanger having a plurality of outer heat extraction fins extending outward from an outer surface of the tank, the outer heat extraction fins in fluid communication with the ambient air; and a fan for moving ambient air through both the active and passive heat exchangers, the fan first passing ambient air through the passive heat exchanger and then passing the air through the active heat exchanger.
 18. The fluid storage tank of claim 16, wherein the passive heat exchanger further includes a first outer shroud portion attached to the tank bounding at least part of a first air flow path having a first outlet generally adjacent the fan and a first inlet spaced away from the fan, the passive heat exchanger further including a first plurality of spaced apart outer heat extraction fins extending outward from the tank, the first plurality of spaced apart outer heat extraction fins interposed between the first inlet and the first outlet along the air flow path and positioned between the first shroud portion and the tank, each of the first plurality of outer heat extraction fins including at least one aperture through which the first air flow path passes as the first air flow path extends from the first inlet to the first outlet; and wherein the passive heat exchanger further includes a second outer shroud portion attached to the tank bounding at least part of a second air flow path having a second outlet generally adjacent the fan and a second inlet spaced away from the fan, the passive heat exchanger further including a second plurality of outer heat extraction fins extending outward from the tank, the second plurality of outer heat extraction fins interposed between the second inlet and the second outlet along the air flow path and positioned between the second shroud portion and the tank, each of the second plurality of outer heat extraction fins including at least one aperture through which the second air flow path passes as the second air flow path extends from the second inlet to the second outlet.
 19. The fluid storage tank of claim 18, further including a plurality of inner heat extraction fins internal to the tank, each of the plurality of inner heat extraction fins being aligned with a corresponding one of the plurality of outer heat extraction fins.
 20. A method of extracting heat from a fluid comprising: passing the fluid through an active heat exchanger that is external to a storage tank for housing the fluid, the active heat exchanger in fluid communication with ambient air surrounding the fluid storage tank; dispensing the fluid into the storage tank after passing it through the active heat exchanger; passing the ambient air through a passive heat exchanger thermally connected to the storage tank; and passing the ambient air through the active heat exchanger after passing it through the passive heat exchanger.
 21. The method of claim 20, wherein passing the ambient air through a passive heat exchanger thermally connected to the storage tank; and passing the ambient air through the active heat exchanger after passing it through the passive heat exchanger are performed by a same fan. 